I use a paint brush style brush to clean the areas that are not cut out (the parts that you can't stick your finger through).
I also use a wheel woolie style brush (I use the smallest one in this set) to clean the cut out honeycomb pieces. They're also great for cleaning rims.
As for the cleaner, either a normal car soap/water mix would do, or if you need a bit more cleaning power, I would recommend using Meguiar's All Purpose Cleaner diluted with water 4:1.
I use the pressure washer (rinse --> snow foam --> rinse) its pretty much enough for me. Just aim the washer nozzle on the area and it should get cleaned